1. Field of the Invention
This invention relates to a cooling system controller for internal combustion engines.
2. Prior Art
It is a daily experience matter that the heating efficiency of a heater is not high at the time immediately after starting up the engine of vehicles. This is because, as stated in the Japanese Laid-open Utility Model Bulletin Jitsu-kai-sho No. 59-139516 (139516/1984), conventional heaters for vehicles use the engine cooling water as the heat source, and consequently, the heater does not supply warmed air until the time when the temperature of cooling water becomes fully high. Namely, the warm-up character of engine has a great influence on the efficiency of heater.
A device which intends to improve the efficiency of heater is disclosed in the Japanese Laid-open Patent Bulletin Toku-kai-sho No. 60-19912. The above improvement relates to a heater for an engine having two separated cooling water circuits, that is, a circuit including a water jacket provided at the cylinder-head side and a circuit including a water jacket provided at the cylinder-block side. In the conventional heaters such as mentioned in the above literature, the heater circuit is by-passed from the cylinder-block side circuit, this is because, in the two-circuits cooling system, the temperature at the head side is generally maintained lower than the temperature at the block side. But, at the time immediately after starting up the engine, the rise of temperature is more rapid at the head side than at the block side, as the head side is positioned more closely to the combustion chamber which is the main heat-generating portion. Therefore, as far as concerned with the heating effect, the conventional heater of aforementioned type is disadvantageous. Incidentally, the heating effects can be improved by combining the bypass valve disclosed in the prior art of said Jitsu-kai-sho No. 59-139516 with the bypass in the circuit on the block side disclosed in another prior art of said Toku-kai-sho No. 60-19912. By this way, the flow rate of the heater circuit can be increased and the heat radiating efficiency of the heater radiator can be improved by closing the bypass. But the amount of heat radiated from the heater cannot be greater than the amount of heat the cooling water receives from the heat generating section. It is also clear that the water on the heat side is at a higher temperature because the greatest portion of the heat generated immediately after start-up is from around the combustion chamber. Thus, the above improvement cannot but be disadvantageous.